There are several approaches for treating female urinary incontinence. One approach involves the submucosal injection of a biocompatible bulking agent into tissue sites adjacent the urethral canal, and/or the bladder neck in order to modify the shape of the tissue sites and/or to provide for improved closure or occlusion between the urethra and the bladder. One particularly suitable bulking agent for this application is sold under the brand name Durasphere® EXP, and is manufactured by Carbon Medical Technologies, St. Paul Minn.
U.S. Pat. Nos. 6,277,392 (Klein et al.) and 5,451,406 (Lawin et al.), both herein incorporated by reference, describe how bulking agent may be submucosally injected using a suitably sized and shaped needle, which is connected to a syringe containing the bulking agent. The needle may be inserted into the patient either outside of and adjacent to, or directly into, the urethra. The tip of the needle may then be positioned in a submucosal tissue site adjacent the urethral canal and/or bladder neck. The bulking agent may then be injected into the submucosal tissue site. The process is normally repeated several times around the circumference of the urethra. An endoscope may be used to view the patient's urethra during the process.
Clinicians face several challenges in performing this process. One challenge is determining the proper placement of an injection guide device and hence the injection needle. Some injection guide devices require visualization and possible trial and error in order to properly set the depth of the guide device, so as to accurately locate the injection target along the urethral wall. Another challenge is injecting the bulking agent at the correct depth into the urethral wall. If the bulking agent is injected too close to the surface, the bulking agent may rupture through the urethra tissue and into the canal. If the bulking agent is injected too far beneath the surface, the bulking agent may be ineffective. Some devices require rather specialized support accessories, such as a ready source of vacuum or visualization equipment, which may be common in some medical specialists' offices, but may not be available to all practitioners.
What would be desirable is a device for injecting bulking agent that can reliably and repeatedly inject the bulking agent at the proper location, with little need for complex added equipment, and not require undue complexity in manipulating the device.